Beijing on Friday urged the United States not to allow Taiwan’s president to travel through US territory en route to the island’s diplomatic allies in the Pacific, a sensitive visit ahead of US President Donald Trump’s trip to China.

Beijing considers democratic Taiwan to be a wayward province ineligible for state-to-state relations and has never renounced the use of force to bring the island under its control.

The mainland regularly calls Taiwan the most sensitive and important issue between it and the United States, and Beijing always complains to Washington about transit stops by Taiwanese presidents.

Taiwanese President Tsai Ing-wen is expected to depart on Saturday for a week-long trip to three Pacific island allies – Tuvalu, the Solomon Islands and the Marshall Islands – transiting via Honolulu and Guam.

The trip comes less than two weeks before Trump is due to visit China. The US president angered Beijing last December by taking a telephone call from Tsai soon after he won the election.

China had made “stern representations” to the US over the matter, foreign ministry spokesman Geng Shuang said, urging the United States to strictly abide by the “one China” policy.

China hopes the US did “not allow her to transit, not send any wrong signals to Taiwan independence forces and take real actions to protect the overall picture of China-US relations and peace and stability in the Taiwan Strait”, Geng said.

The trip to the United States will be Tsai’s second this year. In January she stopped over in Houston and San Francisco on her way to and from Latin America, visiting the headquarters of micro-messaging service Twitter, which is blocked in China, while in California.

In Houston, she met Republican US Senator Ted Cruz and Texas governor Greg Abbott. She also spoke by telephone with US Senator John McCain, head of the powerful Senate Committee on Armed Services.